12 X 8 X 2" Granite Surface Plate Grade B 0 Ledge

12 X 8 X 2" Granite Surface Plate Grade B 0 Ledge ~ Harder than steel and does not nick or burr. ~ Surface plates are checked by an auto-collimator for overall accuracy assurance. ~ Accuracy is ±0001". ~ Granite surface plates meet or exceed Federal Specifications GGG-P-463C. ~ Includes a certificate of inspection. ~ Note that these are not NIST traceable.